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Photo Gallery: Brain

Human Brain

Photograph by Fred Hossler/Getty Images

The human brain is a 3-pound (1.4-kilogram) mass of jelly-like fats and tissues—yet it's the most complex of all known living structures. Up to one trillion nerve cells work together and coordinate the physical actions and mental processes that set humans apart from other species.

Brain and Cervical Spinal Cord

Image by 3D4Medical.com/Getty Images

A rear view of the skull reveals the brain and the cervical spinal cord, which function together as the central nervous system. The remarkable apparatus uses motor neurons to control the body's many muscles and enables humans to perform myriad physical activities.

Brain's Neural Pathways

Image by 3D4Medical.com/Getty Images

The human brain may contain up to one trillion neurons. These nerve cells are interconnected, as shown in this microscopic image, so that they can transmit electrical impulses—and information—to other cells.

Brain MRI Scan

Photograph by Ken Glaser/Corbis

Magnetic resonance imaging (MRI) techniques provide an extremely detailed, 3-D view of a living brain. The technique is critical for identifying abnormalities such as tumors, spotting the warning signs of some brain diseases, and revealing the extent of trauma from strokes.

Slice of Human Brain

Photograph by Cary Wolinsky

Thanks to precision cutting techniques, researchers are able to examine a paper-thin slice of human brain. Surgeons can also cut living brains without fear of hurting their patients—the organ is incapable of feeling pain.

Brain Surgery Patient

Photograph by Joe McNally/Getty Images

A Baltimore, Maryland, epileptic patient performs tests designed to identify the source of his seizures. Surgeons placed electrodes in his brain that will record which parts of the organ become active when he performs a variety of physical and mental tasks.